


A Matter of Biology

by museaway



Category: Star Trek: The Original Series, Star Trek: The Original Series (Movies)
Genre: Between TMP and WoK, Established Relationship, Fluff, Gorgeous fanart by anifanatical, M/M, Pon Farr, Spock being amorous, sweetheart challenge
Language: English
Status: Completed
Published: 2014-02-07
Updated: 2014-02-07
Packaged: 2018-01-11 12:53:45
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,292
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1173307
Author URL: https://archiveofourown.org/users/museaway/pseuds/museaway
Summary: <blockquote class="userstuff">
              <p>In retrospect, Jim supposed he should have noticed the signs that something was, well, <em>off</em> with Spock.</p>
            </blockquote>





	A Matter of Biology

**Author's Note:**

  * For [anifanatical](https://archiveofourown.org/users/anifanatical/gifts).



> **The original prompt:** Can someone please please please write a fluffy Pon Farr fic where Spock is already bonded to Jim and his “being stripped of logic” just means he gradually starts being blatantly amorous in front of everyone for about a week??? And Jim is a blushy pile of mush despite himself???
> 
> For anifanatical, who makes such happy space husbands fanart. You make my Tumblr dash a happier place. *sigh* 
> 
> Thank you to [Juno](http://archiveofourown.org/users/junomagic) for the beta!
> 
>  _Note:_ I am no expert in Vulcan, but I studied for two days to try and get the phrasing correct. If you spot a mistake, please let me know so that I can correct it!

In retrospect, Jim supposed he should have noticed the signs that something was, well, _off_ with Spock. 

Now that he thought long and hard about it, Jim could just about pinpoint the day the changes started, not quite a year following the V'Ger incident. But it would've seemed absurd to question it when Spock had taken Jim's arm on the sidewalk in front of their apartment building on a Sunday after breakfast. Who was Jim to complain when Spock placed a hand on the small of Jim's back while they received orders from Admiral Nogura regarding the _Enterprise_ 's handover? Everyone forgot to eat dinner now and then, especially when caught up in a good book. Jim was pleased his reading habits were rubbing off on Spock. Nevermind that Spock rarely indulged in fiction and had never, in Jim's memory, forgotten anything. And it would've been silly to call Bones to complain that Spock had leaned his head against Jim's as they both sat up in bed reading, or when he reached for Jim through their bond when they were apart for no more than an hour. 

V'Ger had altered Spock; impressions of its empty logic had passed to Jim during melds. Jim often replayed the memory of Spock's hand clasping his in sickbay, and he convinced himself that Spock's burgeoning affection was merely a first attempt in accepting his humanity. Jim cherished the small touches which grew more frequent and less innocent over a period of several days. The gestures were no different from the many ways he touched Spock. And if the increase in physical displays of affection happened to be accompanied by an increase in sex drive, well, Jim would be the last one to complain.

He found himself smiling more, sleeping restfully, waking earlier. When he came home at the end of a long day at headquarters to find Spock seated in front of the fire, it was like receiving his stripes all over again. He would drape himself over Spock's back, whisper "hello" into his ear, and Spock would lean back to kiss him. Inside of a week, the kisses went from innocent gestures of greeting to Jim laid out shirtless on the floor next to the fireplace, and Spock sweetly whispering _ashal-veh_. Inwardly, Jim celebrated that he had finally cracked that stiff, desert-bred propriety. 

He should have known. 

***

It was a routine training exercise, designed to identify weaknesses in Captain Spock's ability to command. The ship would travel for a single day at warp three, engage in a simulated hostile encounter, then take a leisurely ride back. Technically, Jim shouldn't have been the one to oversee it. Nogura agreed, but Spock had assured him that, as a Vulcan, he was capable of separating his personal and professional lives. 

Jim felt compelled to live up to the challenge and assumed that Spock would put aside his newfound behavior for one day. But Spock held Jim's arm as they walked to headquarters that morning, and he stood behind him with both hands on Jim's hips as they waited for their turn in the transporter. 

"Morning," Jim greeted the crew who filed in to wait with them. Uhura met his eyes and widened both of hers, nodding approvingly. Jim looked down and attempted to suppress a smile. Spock's hands gently pulled at Jim's waist and inched him backwards until he was flush against Spock's hips. Spock pressed forward just enough that Jim could feel his arousal. Jim about choked when Sulu said, "Good morning, Admiral, Captain."

"Mr. Sulu," Jim managed as Spock flexed...something, and a voice in Jim's mind announced, _I desire you_. He sent back a rebuke, a promise of _later_ , and pulled out his comm. It gave him the excuse to step away and pointedly avoid Spock's gaze. He stood beside the control panel and feigned checking for messages until the technician arrived and waved them onto the platform. Spock smiled at him as they dematerialized and again as they took their positions on the bridge, but they shortly settled into a familiar, professional routine. 

It was surreal, watching Spock assume the captain's chair, standing beside him as an observer instead of the commanding officer. Jim felt a pang of sadness, a bittersweet ache at the realization that his lady was no longer his. She belonged to a new captain. He loved that captain, knew the ship would be safe in his hands, but this was home: standing on the bridge with Spock, the glittering black of space waiting for them. Not for the first time, he regretted that he had ignored Bones's advice and accepted the promotion.

Ah, well. What was it that Spock said? _Kaiidth_. He would stand it. 

The first part of the trip was uneventful. Spock frequently requested updates from Sulu about their location. The need to observe Spock was routine, frankly unnecessary. That was the only reason Jim had agreed to oversee it himself. Spock was familiar with the protocol of command, comfortable in the role even if he did prefer a first officer's position. Jim was thinking about heading down to the mess, perusing the lunch offerings. He took a step toward the turbolift and felt a distinct tug on the bond. Spock turned to look at Jim over his shoulder. 

"Are you going somewhere, Admiral?" he asked.

"I'm starved," Jim said. "Thought I'd get a sandwich."

"I will join you," Spock announced and turned the conn over to Sulu. He was at Jim's side in seconds and held out a hand. Jim was surprised but took it. 

"Jim," Spock said quietly and led him into the lift. Spock continued to hold Jim's hand, stroking along his veins and the rise of his knuckles until the lift's movement stopped and the doors opened. 

"Shall we?" Jim asked and attempted to pull his hand away, but Spock kept a firm grasp. Jim considered that Spock was acting as he wished they could have done when they first served together. As the senior officers on board, it technically went against protocol, but what was the harm in it? This wasn't a mission, just a training exercise, and it would be over tomorrow. If Spock wanted to hold his hand on their way into the mess, did it matter if people saw? The entire crew knew they were married; a good number of them had been present for the ceremony. Jim relaxed and squeezed Spock's hand affectionately when the doors opened.

"Have I told you that you're going to be an excellent captain?"

"You have," Spock confirmed as they walked through the corridor, "though I do not tire of hearing it."

"Since when do you willingly accept a compliment?"

"You are my former captain and my chosen mate," Spock said. "I am honored that you think so highly of me."

Jim could count on one hand the number of times Spock had said something like that to him. Maybe Spock was worried how Jim would take the handover. He'd probably asked Uhura for advice. That would explain why she'd smiled at them in the transporter room. _Of course_ , Jim thought, and he was bolstered by the idea of his logical better half going to such lengths to reassure him. 

When they were seated, and Jim was halfway through his sandwich, he felt Spock's foot come to rest next to his beneath the table. He hadn't played footsie since his academy days and laughed into his coffee. There were only a few other people in the mess, and no one was looking in their direction. Jim raised an eyebrow in challenge. Spock sent him an explicit mental image, and the sandwich lost its appeal. Jim folded his hands together and rested his elbows on the table. Spock rubbed his instep, and Jim gave him a smile in return. Seemingly encouraged, Spock tilted his head and began to stroke the back of Jim's calf with the toe of his boot. It was easily the most flirtatious act Spock had ever performed outside their apartment. He looked exceedingly pleased with himself. Jim would have to send Uhura flowers.

"We should get back to the bridge," he said, noting the time. 

"Where you go, I go," Spock said, and the sincerity in his tone made Jim pause. 

"Are you alright?" he asked quietly. 

"Why would you presume I am not?"

Jim shrugged and balled up his napkin, leaving it on the tray for a yeoman to clear. He brushed crumbs from his uniform and stood up.

"You're in unusually high spirits. And you look a bit flushed."

"I am with _you_."

"Ah," Jim said and nodded to the door, fighting to keep the scowl off of his face. They walked quietly side by side back to the lift. Spock gave the order for the bridge and stroked Jim's arm. 

"I'm fine about the handover," Jim told him, reaching up to smooth Spock's bangs. "Really."

"You are handling it remarkably well."

"And you don't need to be concerned about me when you're gone. We've been apart before."

"Indeed," Spock said. The lift slowed. Jim expected Spock to release his arm, but he didn't. Instead, he slipped an arm around Jim's waist and practically escorted him.

"Captain on the bridge." 

The announcement wasn't for him. He felt a twinge of disappointment but tried to keep his face neutral. Spock's arm tightened around him as they walked to the captain's chair. He sat down and patted the arm rest. Jim shook his head and remained standing. Spock took his hand instead and stroked it idly as he began the same line of questions he had asked before lunch: status, any changes in course, anything relevant to report on the sensors or via transmission. 

"Very good, Mr. Sulu," Spock said and sat back. 

"What's gotten into you?" Jim asked as Spock turned Jim's hand over and began tracing the lines on his palm. It was something he did often, but only when it was just the two of them. Jim felt his face grow warm; he jerked his hand away. "If you're trying to prove a point, it won't work."

"What point do you believe I am trying to make?" Spock asked, wrapping his fingers around Jim's wrist instead. He felt unusually warm, almost close to Jim's own body temperature, but he was wearing his thermal. Jim had seen him put it on that morning. He pursed his lips. 

"You were the one who insisted we could keep work and our private lives separate. I may not be a Vulcan, but I can keep my hands to myself. Are you testing my ability to resist you?"

"Hardly," Spock said and pushed a wave of fondness at him. "I am hoping you will give in to my advances."

It was romantic and frustrating and absolutely not the time or place for such a declaration, but Jim flushed despite himself.

"I realize this exercise is just a formality," he said, frowning to conceal his grin, "but let's remember we're both high-ranking Starfleet officers until shift ends."

"Yes, Jim," Spock said with a sigh and folded his hands on his lap. 

"Good," Jim said and put several paces between himself and Spock. He shook off the uneasy feeling which pooled in his stomach and lapped the bridge, checking on each station. Uhura gave him a sympathetic look as he passed; he patted her on the shoulder. He stopped behind Sulu and watched the blinking light patterns on the navigation dash, the blur of stars on the viewscreen. He was keenly aware of Spock's melancholy, of an intense longing that wrapped itself around his brain. 

Had Spock eaten sugar without realizing it? Jim remembered a shore leave during the last year of their mission when Spock had drunk a cup of tea, not realizing it had been laced with the extract of a native plant. The afternoon had been similar, with Jim having to extract himself from Spock's lap three times. He'd been with Spock since they woke up, knew he'd drunk only a cup of Vulcan spice tea and ate a somewhat stale loaf of _kreyla_. They'd been running late (due  to an incident in the shower that Spock had initiated which, now that Jim thought about it, was out of character) so Spock hadn't even bothered with jam. It couldn't be sugar. 

A tone sounded from Sulu's panel, and several of the indicator lights glowed yellow. 

"Captain," Sulu said, "arrival at our destination in one hour, thirty minutes."

"Acknowledged," Spock said. Jim felt him approach, looked down to see Spock's arms snake around him. 

"I hope you will be proud of me," Spock spoke into his ear. 

"You are the captain of a Federation starship," Jim whispered firmly. He pushed Spock's hands away and turned around. "I expect you to act like it."

" _Ashal-veh_ ," Spock murmured and brushed Jim's meld points. At her console, Uhura cleared her throat and took an interest in dusting her screen. This wasn't right. Jim could excuse what happened in the mess, and he could almost believe that Spock might touch his hand on the bridge, but something had to be wrong for him to act this way. 

"Captain Spock," Jim said clearly, turning his head so Spock's hand fell away. "Conference room. Now."

***

Jim firmly closed the door behind them and engaged the privacy lock before rounding on Spock. 

"You've got one minute to tell me what's going on," he said firmly, "or I'll relieve you of duty. Are you sick?" 

"Jim." Spock's voice was warm. He touched the front of Jim's uniform, fingering the fastenings. A faint smile hovered at the corner of his lips. "I was certain that you had discerned the issue."

"You've gone mad?"

Spock shook his head. "My logic is gone."

"Your logic," Jim repeated, "is _gone_?"

"I believe it is the _pon farr_."

Jim frowned, counting the time since that journey to Vulcan. He tried to recall his own age: he was forty--no, he was forty-one, because Spock had just turned forty-four. Had it really been seven years already? Jim thought of a _plomeek_ stain which had taken operations three types of cleaner to remove. He heard the deep ring of the ceremonial gong, the bright shaking of bells, the pride in T'Pau's voice. He replayed Spock's frequent mood swings, his uncharacteristic deception, the hardness in his eyes as he tightened the _ahn'woon_ around Jim's throat. 

Was it possible that the same biological urge which had nearly driven Spock to madness could be responsible for...this? He thought of Spock's flushed appearance, his sudden forgetfulness, his amorous behavior, the increase in sex drive. Jim felt some of the anger abate, but his lips parted, and it was many seconds before he was able to reply. 

"But you didn't act this way the last time," he said finally. 

"I was not bonded to you," Spock murmured and traced a finger along Jim's jaw. Jim's stomach fluttered despite himself. 

"You had a bond with T'Pring," he countered, but he tilted his head to the right as Spock stepped closer and lowered his mouth to Jim's neck. 

"But you will not challenge," Spock said, kissing from below Jim's ear to the hollow of his throat. "There is no threat to the bond."

"You didn't know she would challenge."

"I must have sensed it," Spock said. He grazed Jim's collarbone with his teeth. "I want to remove your clothing."

"We can't do this here," Jim hissed. He batted at Spock's hands and walked quickly to the opposite side of the room. "You have to get ahold of yourself."

"Not possible," Spock said. "My logic will not return until the _pon farr_ is satisfied."

"We're on a training mission!"

"Mr. Sulu is capable of commanding the ship back to Earth."

"We haven't even begun the simulation! Are you actually proposing that we turn the conn over to Sulu and hole up in the guest quarters?"

"My quarters would be preferable," Spock said, "but I will be content in any location, as long as you are with me."

"Can't you wait a day? A _day_ , Spock, until we're back on Earth."

"Negative," Spock said. "I regret that I did not request a delay of the training mission, but as you know, my logic is compromised. I knew you would be with me, and I saw no reason to inconvenience the crew."

Jim bit the inside of his lip and exhaled. 

"You are an aesthetically pleasing man, Jim."

"Spock..."

"I wish to engage in sexual intercourse with you."

"Yes," Jim said and rubbed his forehead as though it would block the thoughts Spock was projecting. "Yes, I'm aware of that." He glanced to the door, nodded, and looked back at Spock, meeting his eyes. "Can't you...meditate?"

"I find I am unable to concentrate," Spock said. "Your mind is a great distraction, as is your form."

Jim perched on the edge of the conference table. "So this is why you've been so...tactile lately."

"Yes."

"I see," Jim said.

"You are disappointed," Spock observed. 

"I was hoping it was a permanent change," Jim admitted. 

"I regret that I do not provide the level of affection you deserve."

Jim exhaled and stared at his hands. He touched the fourth finger on his left hand, conspicuously devoid of a ring. The metal, Spock said, might affect his telepathy, so Jim had chosen not to wear one either. 

"I don't think that," he said. 

"You wish I were more human."

"I wish you were more comfortable with the fact that you're half human," Jim corrected, "but I've never been unhappy with our relationship."

"I am glad."

Jim chuckled, because what else was there to do? He sighed and held out a hand. Spock came to him, tucking his face into Jim's neck and shoulder. His forehead connected with Jim's bare neck, and Jim became aware of the fever burning through him. Jim held him, able to feel the smile against his skin. Was it in his head, or could he actually discern the impression of teeth? It didn't matter. Spock was happy, and Jim would see him safely through the pon farr. No challenge, no simulated death, just the two of them, for however long it took. Spock was hard against his hipbone, grinding against him slowly. Jim trailed a hand down his spine. 

"If I go to the bridge to take care of a few details," Jim asked against Spock's hair, "will you stay here?"

"No," Spock said. "I find I am unwilling to allow you out of my sight."

"I was afraid you'd say that," Jim said, half to himself. He pulled out his comm. "Kirk to bridge."

"Sulu here."

"Mr. Spock is sick and unable to complete the simulation. It will be necessary to reschedule. Set a return course to Earth immediately."

"Yes, Admiral."

"Kirk out," Jim said and snapped the communicator closed. "So. Your quarters?"

***

Nogura wasn't thrilled when Jim informed him they'd need to reschedule, but he hadn't questioned Spock's condition. Jim described it as a "Vulcan ailment," and they'd left it at that. The twelve hours they spent sequestered in Spock's quarters had slaked his desire somewhat, but it was a long aircar ride home from headquarters. (Walking was definitely out.)

Jim had always expected the _pon farr_ to be rough, a little brutal, maybe even punishing. But Spock had been as gentle as he usually was when he held Jim to his chest. He whispered sweet nothings into Jim's ear: " _K'diwa_ _, k’hat’n’dlawa. Saudau tu maut vaksurik, adun t'nash-veh_." He smiled as rolled Jim onto his back, worked him open, and sank into him with a cry on the living room floor. When they finally made it to the bedroom, he gathered Jim to him and stroked his face, as if he were memorizing every pore and scar and wrinkle. 

" _T'hy'la_ ," he whispered. " _T'hy'la_."

Jim's uniform top was a casualty of the situation, left in two pieces just inside the front door. Jim found it there almost a full day later when he got up to shower and fix himself something to eat. The hot water worked out some of the residual soreness. Jim dressed quietly; Spock was still sleeping under a mound of blankets. Jim steeped a cup of tea for him while the coffee brewed and returned to the bedroom with a tray that also contained two bowls of oatmeal. He set it on the bedside table and stretched out alongside Spock on the bed, trailing fingers over his arm until he stirred. 

"Jim?" Spock asked, pushing up on one elbow. His eyes darted around the room before settling on Jim's face. "Are we at home?"

"Oh, sweetheart," Jim murmured and brushed Spock's bangs from his forehead. "Don't you remember?"

"I recall leaving for the observation," Spock began. "I recall being on the bridge with you, and I recall..." He closed his mouth. It settled into a line, and he furrowed his brow. 

"Apologies are illogical," Jim said, "so don't even bother."

"I presume you were able to reschedule."

"I've taken care of the details," Jim said. "Lie back down."

Spock complied, lifting a hand to Jim's face and resting it against his cheek. "Did I injure you?"

Jim shook his head. "No," he said, and it struck him that Spock's palm was cool again. He nuzzled it, pressing a kiss to the center. "How are you feeling?"

"I am fine," Spock answered, "though somewhat embarrassed."

"Nothing to be embarrassed about," Jim said. "It's a matter of biology, after all."

"I was not myself." 

"You were sweet."

"You would be right to reprimand me for my behavior."

"For something you couldn't control?" Jim asked. He shook his head and kissed Spock quickly, then arranged the sheet over both of them. "Breakfast?"

"I am hungry," Spock admitted, and they settled into their typical routine.

***

Spock was withdrawn most of the morning, going over messages he had received and responding to inquiries from students. He had dressed in austere black robes and sat stiffly at his desk. Jim reheated his tea twice before he gave up and settled into a chair in front of the fireplace. He pulled a throw over his legs and read for about an hour before his lower back began to ache. He rose and stretched, leaving the blanket balled up on the chair, and went to the window. 

The apartment had been out of his price range when he first found it, but Jim had insisted because of the view. It looked out over the Pacific, with a wide expanse of sky. Jim had never minded that the apartment itself was small. It had a living room, kitchen, bedroom, and a raised platform near the window where they ate dinner. He'd been worried that they would need to find something larger when Spock moved in, but Spock had been content with the size. They talked about getting a place on Vulcan too, but they hadn't made a trip to peruse real estate yet. Amanda never failed to mention it when they spoke.

Below him, the Pacific rolled in and broke against the rocky shore. He raised his hand to the glass. The shock of cold against his fingertips made him shiver.

"Guess it's too cold for a walk," he said. In his peripheral vision, Spock lifted his head. 

"It would be beneficial for us to exercise," he said. "I will fetch your coat."

***

They walked casually along the waterfront. Jim's hands were thrust into his coat pockets, and his arm brushed against Spock's occasionally. They didn't talk much, but Jim was content with the quiet.

Eventually, they came upon a favorite spot, where Jim often leaned against the railing to watch the water. He gripped the railing and leaned forward on his arms, feeling his arm and back muscles strain. He was still sore from the last two days and reluctantly eased up, resigning to rest his palms on the metal. 

"Jim?" Spock inquired, standing to his right, a column of black. His hat fit snugly over his ears, and the full-length coat covered him below his knees. The tip of his nose was green with cold. Jim could feel Spock prodding him through the bond, which was brighter than he had ever felt it. He sighed.

"It wasn't what I expected," he said. 

"Nor I."

"I thought you would behave the same as last time." He cleared his throat and watched the white crest of a wave dissolve into foam. 

"I shared your prediction."

Jim thought of the last week, of how often Spock had touched him, at the unbridled affection on his face whenever he'd looked in Jim's direction. _Well_ , he told himself, at least he would have that every seven years. He thought he better understood Amanda's silent exasperation. It was not that she longed to know Sarek's tenderness; rather, she had experienced it and had it taken from her. 

"Seven years, hm?" Jim asked. He smiled over his shoulder at Spock, who looked down. Jim chuckled and shook his head. "I love you, you know."

Spock flushed, as he always did when Jim declared himself, but he stepped closer, until there wasn't any space between them. He placed a gloved hand atop Jim's on the railing. It was enough. God, it was enough. Jim felt an unexpected sting in his eyes, but he smiled through it as Spock's other hand came to rest on his back. He leaned into the touch, memorizing it and the contented pulse of energy between them. Spock lowered his face to Jim's neck and kissed it once, pulling back just enough to whisper: "I am happy."

  
Beautiful art by [anifanatical](http://anifanatical.tumblr.com)

**Author's Note:**

> Thank you for reading! You can also find me [on Tumblr](http://museaway.tumblr.com) and [on Livejournal](http://museaway.livejournal.com).


End file.
